This invention relates to a piston-cylinder unit as it is typically used in cranes, for instance truck or crawler cranes.
Especially in crane construction, problems frequently arise where signals and electrical connections must be guided to places located far away. Sometimes, these points also are connected with the basic machine in a length-variable manner, such as when supporting a crane. When supporting a crane, one would like to know for instance which vertical forces are absorbed by props. For this purpose corresponding sensors are provided. One possible solution consists in that at the end of the so-called supporting foot a force sensor is provided. This can be taken for instance from EP 1 366 253 B1, in which a sensor is provided between the supporting beam and the supporting plate or at the end of the supporting beam. From DE 10 32 03 82 A1 it is known to provide a cable connection between sliding beam and supporting plate.
The sensors provided in the piston-cylinder unit supply data which in use in a truck or crawler crane must be supplied to the crane controller. In addition, the sensor requires energy. The connection known from the prior art has great problems, since the cables generally are guided freely and thus are exposed to damages. As far as the connecting cables are used in the support of a truck or crawler crane, it must be taken into account that this support can be shifted both in horizontal direction (by the sliding beams) and in vertical direction (by the supporting cylinders).